Filter with a bypass mechanism for a hydraulic system

Abstract

A reservoir for a hydraulic system includes a housing having an inlet and an outlet. The inlet is adapted to receive an incoming fluid and is formed within an inlet tube that extends into the housing. A filter within the housing, includes a filter element, defining an inner filter chamber, and includes an inlet opening encompassing the inlet tube that extends into the housing. The inlet opening allows the incoming fluid to enter the inner filter chamber for filtration. A base wall around the inlet opening includes a guide step that guides a relative movement between the reservoir and the filter. A relative movement between the filter and the reservoir facilitates the base wall, the guide step, and the inlet tube, to co-operate and establish a bypass route for selectively allowing the incoming fluid to bypass the filter, depending upon a predetermined differential pressure between the inlet and the outlet.

We claim: 
     
         1 . A reservoir for a hydraulic system comprising:
 a housing, having an inlet tube extending into the housing;   a filter basket disposed within the housing, the filter basket including
 a filter element, generally cylindrical in form, defining an inner filter chamber, the filter basket being sized and positioned for sliding movement on the inlet tube, 
 a base wall, including
 an upper base layer and a lower base layer, the base layers being spaced apart to define a bypass passage; and 
 
   resilient means mounted between the filter basket and the housing, having a spring force chosen to bias the filter basket between
 a normal operating position, wherein the upper base layer blocks the bypass passage; and 
 a bypass operating position wherein the upper base layer does not block the bypass passage. 
   
     
     
         2 . The reservoir of  claim 1  further comprising at least one slosh baffle on the base wall, the slosh baffle spaced from the filter element to define a dead flow zone positioned to receive contaminants filtered from the fluid by the filter element and adapted to create a stagnant flow zone between the slosh baffle and the filter element. 
     
     
         3 . The reservoir of  claim 2 , wherein the base wall has a central wall section disposed around the inlet opening and a peripheral wall section remote to the inlet opening, wherein the central wall section projects further into the inner filter chamber than the peripheral wall section, while the slosh baffle connects the central wall section to the peripheral wall section. 
     
     
         4 . The reservoir of  claim 1  wherein the resilient means is a spring element supported against an inner side of the housing, biasing the filter against the inlet, wherein the filter is mounted movably along an axis of the housing therein, such that: 
     
     
         5 . The reservoir of  claim 5 , wherein the spring element is an arc spring formed from a plurality of bending elements. 
     
     
         6 . The reservoir of  claim 5  further comprising a filler opening in the housing along which the spring element is disposed co-axially. 
     
     
         7 . The reservoir of  claim 1 , wherein the base wall includes
 an inlet opening formed centrally on the base wall, sized and dimensioned for sliding vertical movement on the inlet tube, the length of the inlet opening being generally equal to that of the inlet tube; and   wherein
 the upper base layer has an inner horizontal portion extending radially from the inlet opening, a vertical portion extending vertically downward from the outer end of the inner horizontal portion; and an outer horizontal portion extending radially outward from the lower end of the vertical portion, the outer end of the outer horizontal portion being attached to the lower end of the filter element; 
 the lower base layer has a vertical portion forming the inner surface of the inlet opening, extending vertically below the filter element, and a horizontal portion extending to a point below the end of the upper base layer outer horizontal portion; 
   
     
     
         8 . The reservoir of  claim 1 , wherein the filter includes fine filter and a coarse filter connected in series, the fine filter being downstream from the coarse filter. 
     
     
         9 . The reservoir of  claim 8 , wherein the bypass channel bypasses the fine filter but does not bypass the coarse filter. 
     
     
         10 . The reservoir of  claim 8 , wherein the bypass channel bypasses both the coarse filter and the fine filter. 
     
     
         11 . A reservoir for a hydraulic system comprising:
 a housing, having an inlet tube extending into the housing;   a filter basket disposed within the housing, the filter basket including
 a filter element, generally cylindrical in form, defining an inner filter chamber, 
 a base wall, including
 a slosh baffle, spaced from the filter element to define a dead flow zone, positioned to receive contaminants filtered from the fluid by the filter element, and adapted to create a stagnant flow zone between the slosh baffle and the filter element; 
 an inlet opening formed centrally on the base wall, sized and dimensioned for sliding vertical movement on the inlet tube, the length of the inlet opening being generally equal to that of the inlet tube; 
 an upper base layer having an inner horizontal portion extending radially from the inlet opening, a vertical portion extending vertically downward from the outer end of the inner horizontal portion; and an outer horizontal portion extending radially outward from the lower end of the vertical portion, the outer end of the outer horizontal portion being attached to the lower end of the filter element; 
 a lower base layer having a vertical portion forming the inner surface of the inlet opening, extending vertically below the filter element, and a horizontal portion extending to a point below the end of the upper base layer outer horizontal portion; 
 wherein the lower base layer is separated from the upper base layer, defining a bypass passage between the lower base layer and the upper base layer; 
 
   resilient means for vertically biasing the filter basket, mounted between the upper portion of the filter basket and the inner surface of the housing, having a spring force chosen to bias between a normal operating position, wherein
 the normal operating position bias is sufficient to position the filter basket such that the upper base layer blocks the bypass passage; and 
 the bypass operating position bias allows the filter basket to ascend to a position such that the upper base layer is above the bypass passage. 
   
     
     
         12 . The reservoir of  claim 11 , wherein the slosh baffle is disposed concentrically around the inlet opening. 
     
     
         13 . The reservoir of  claim 11 , wherein the base wall has a central wall section disposed around the inlet opening and a peripheral wall section remote to the inlet opening, wherein the central wall section projects further into the inner filter chamber than the peripheral wall section, while the slosh baffle connects the central wall section to the peripheral wall section. 
     
     
         14 . The reservoir of  claim 11  wherein the resilient means is a spring element supported against an inner side of the housing, biasing the filter against the inlet, wherein the filter is mounted movably along an axis of the housing therein, such that: 
     
     
         15 . The reservoir of  claim 14 , wherein the spring element is an arc spring formed from a plurality of bending elements. 
     
     
         16 . The reservoir of  claim 14  further comprising a filler opening in the housing. 
     
     
         17 . The reservoir of  claim 11 , wherein the filter includes a fine filter and a coarse filter connected in series, wherein the fine filter is disposed downstream from the coarse filter. 
     
     
         18 . The reservoir of  claim 17 , wherein the bypass channel bypasses the fine filter. 
     
     
         19 . The reservoir of  claim 17 , wherein the bypass channel bypasses both the coarse filter and the fine filter.